Customizations for default WordPress audio shortcode and embed.

wp-audio-custom.php

<?php
/**
 * Change attribute for WP audio shortcode and embed.
 *
 * Default preload attribute is 'none' which shows time as 'O:OO'.
 * Setting attribute to 'metadata' displays time upon page load.
 *
 * @param  string $html Default audio shortcode HTML output.
 * @return string $html Filtered audio shortcode HTML output.
 */
function my_audio_preload( $html, $atts, $audio, $post_id, $library ) {
    $html = str_replace( 'preload="none"', 'preload="metadata"', $html );

    return $html;
}
add_filter( 'wp_audio_shortcode', 'my_audio_preload', 10, 5 );